I stumbled upon what is described as a ASAHI 500 mm. that was used on an old Pentax K1000. Its thru a friend of a friend of a friend. So, doing a bit of research, I am thinking that its a Asahi SMC Pentax 500 mm f/4.5 K probably a K mount given the K1000, but could be a M42. Does not really matter though.

I know Roy (robar) had one, and was very happy with it till it had some mechanical problem. I think that was pretty odd and shouldn't scare you off, if you can get this at a fair price. It's huge, longer and heavier than my 600mm 5.6.
Roy posted some nice pictures, but I can't find the thread.

Thanks Kjell and Dawg! I was able to call the gentleman today. He had to dig out the camera, and when he found it he started reading the numbers off of it. It seems like he got carried away with the zeros to some extent. It looks like its a SMC Pentax A 50mm either a f2 of f1.2 His cordless phone was going out so, I am going to call back tomorrow. I am thinking its the standard lens that came with the K1000 (the f2 or an upgrade to f1.2). I would not mind acquiring a f1.2 at all.

Thanks Kjell and Dawg! I was able to call the gentleman today. He had to dig out the camera, and when he found it he started reading the numbers off of it. It seems like he got carried away with the zeros to some extent. It looks like its a SMC Pentax A 50mm either a f2 of f1.2 His cordless phone was going out so, I am going to call back tomorrow. I am thinking its the standard lens that came with the K1000 (the f2 or an upgrade to f1.2). I would not mind acquiring a f1.2 at all.

no prob with the 500/4.5..
wonerful lens. prob is it owns you when you go shoot.
only mechanical prob with it started when i dropped it..
pentax USA may have a K mount for it @ about $140..
be sure they have all (16) the parts in stock.